1. Technical Field
This application relates to a catheter and more particularly to a peritoneal dialysis catheter and method of insertion.
2. Background of Related Art
The kidneys are organs which function to extract water and urea, mineral salts, toxins, and other waste products from the blood with filtering units called nephrons. From the nephrons the collected waste is sent to the bladder for excretion. For patients having one or both defective kidneys, the dialysis procedure is life saving because it simulates the function of the kidneys.
Dialysis is a process of diffusing blood across a semi-permeable membrane to remove toxic materials and to maintain fluid, electrolyte and acid based balance in patients having impaired kidney function. Hemodialysis is one well known method of providing renal (kidney) function by circulating blood. Peritoneal dialysis is another known method for cleansing the blood.
In the hemodialysis procedure, blood is withdrawn from the patient's body through a catheter or tube and transported to a dialysis machine, also commonly referred to as a kidney machine. The catheter is typically inserted through the jugular vein and maneuvered into position through the superior vena cava into the right atrium to provide high blood flow. In the dialysis machine, toxins and other waste products diffuse through a semi-permeable membrane into a dialysis fluid closely matching the chemical composition of the blood. The filtered blood, i.e. with the waste products removed, is then returned to the patient's body. In some instances, the catheter may be left in place for as long as sixty days. As can be appreciated, proper access to the patient's blood and transport of the blood to and from the dialysis machine for this extended period of time is critical to hemodialysis.
In peritoneal dialysis, removal of toxic substances is achieved by perfusing chemical solutions (dialysate fluid) through the peritoneal cavity. A catheter is inserted into the patient's abdomen (peritoneal cavity) to deliver dialysate fluid to fill the cavity. The peritoneum, the membrane which lines the abdominal cavity, allows chemical wastes and excess water to diffuse out of the blood and pass into the dialysate fluid, as blood vessels in the peritoneal membrane are exposed to the fluid. Thus, waste products move through the pores in the peritoneal membrane and pass into the dialysate fluid. The catheter then drains the dialysate fluid and waste.
Typically, peritoneal dialysis catheters are inserted as follows:                1. an introducer needle is inserted through a first incision;        2. a guidewire is inserted through the introducer needle into the internal abdominal cavity;        3. the introducer needle is withdrawn leaving the guidewire in place;        4. a tear away sheath and dilator are inserted over the guidewire and through the first incision site to provide an access port for the dialysis catheter into the abdominal cavity;        5. the dilator and guidewire are removed, leaving the tear away sheath in place in the first incision which has been expanded by the dilator;        6. the dialysis catheter is inserted through the tear away sheath and advanced into the peritoneal cavity;        7. the sheath is separated, i.e. split, by pulling the tabs apart, and then pulled upwardly away from the dialysis catheter and removed from the body, leaving the catheter in place;        8. a trocar or tunneling tip is attached to the proximal end of the catheter;        9. the trocar and dialysis catheter are pushed through the tissue to bluntly dissect the subcutaneous tissue to create a subcutaneous tissue tunnel from the first incision to a second incision exiting from the abdomen spaced from the first incision;        10. the trocar is detached from the dialysis catheter leaving the catheter in place extending through the tissue tunnel between the first and second incisions; and        11. the second incision is closed and the dialysis catheter is left in place for the desired period of time.        
Alternatively, in the prior art method the trocar tip can be attached to the distal end of the catheter, the catheter inserted through the second incision, and then tunneled to the first incision. The catheter is then inserted through the tear away sheath.
This multiple step process is time consuming and complicates the surgical procedure. This multiple step process also adds to the cost of the procedure, not only because of the additional surgeon's time but because additional components, such as the tear-away sheath, are required which increases the overall cost of the catheter system. Also, removal of the dilator increases the tendency of the sheath to kink causing difficulties in catheter insertion.
The use of the tear away sheath is also potentially problematic. The tear-away style sheath has lines of weakness to separate the sheath as it is pulled apart by the pull tabs to enable removal of the sheath. However, the sheath can potentially cause damage to the surrounding tissue as it is being pulled apart and can cause infection. Moreover, pulling the sheath laterally can enlarge the incision, thereby increasing the difficulty of closing the incision at the end of the procedure. Also, since the sheath is pulled in the proximal direction for removal, it could pull the catheter proximally as well, thereby pulling it away from the desired site, and requiring repositioning. The edges of the tear away can also lacerate the surgeon's glove and finger.
It would therefore be advantageous if a peritoneal dialysis catheter insertion method could be provided which reduces some of the foregoing procedural steps, thereby decreasing the complexity of the procedure and decreasing the hospital and surgeon costs. It would also be advantageous if such dialysis catheter insertion method could be provided which would be less traumatic and avoid the foregoing problems associated with the use of a tear-away sheath, such as trauma to the surrounding tissue, incision enlargement and dislodgement of the catheter.
Another area of dialysis catheter insertion which needs improvement is guiding the catheter to the target site. Dialysis catheters are composed of flexible tubing to minimize damage to the tissue during insertion and use. This flexibility, however, oftentimes results in kinking of the catheter. This kinking can adversely affect fluid flow. Also, the catheter needs to have some degree of stiffness to enable directing the catheter. The stiffness, however provides its own risks since if the catheter is not properly directed, the catheter can inadvertently be forced against and damage tissue. Several different approaches have been discussed in the prior art to increase stiffness of catheters such as providing a distal tip of stiffer material to guide the catheter as in U.S. Pat. No. 5,957,893, using materials of different durometers in various portions of the catheter (U.S. Pat. No. 5,348,536), placing an additional concentration of material in the tip as in U.S. Pat. No. 4,583,968, or providing reinforcing strips, obturators or tubes within the catheter body to increase the rigidity (e.g. U.S. Pat. Nos. 4,619,643, 4,950,259 5,221,255, 5,221,256, and 5,246,430). The need however exists to improve the balance between flexibility and stiffness. Thus it would be advantageous to provide a catheter with sufficient flexibility to accommodate curves while still having sufficient stiffness to enable guiding the flexible catheter tubing atraumatically through the subcutaneous tissue tunnel and into the abdominal cavity.
It is also desirable to provide the smallest catheter profile, i.e. the smallest outer diameter catheter body. This profile facilitates insertion and facilitates closure of the catheter incision. However, the desire for smaller diameter catheters must be balanced against the need for providing sufficient sized lumens to enable proper fluid flow. Also, a sufficient relationship must be maintained between the size of the lumens and the overall diameter of the catheter to maintain the structural integrity of the catheter.
The need therefore exists for an improved dialysis catheter which facilitates the dialysis procedure. Such catheter would advantageously reduce the catheter insertion time, simplify the catheter insertion process, eliminate the need for a peel-away introducer sheath, reduce unwanted kinking of the catheter during insertion, and strike an optimal balance between overall catheter and lumen size.